The invention relates generally to adhesive dispensing systems, and more particularly to processes for bonding one or more relatively elongated strands to one or more substrates, especially bonding stretched elastic strands to fabrics in the manufacture of bodily fluid absorbing hygienic articles.
It is often desirable to bond or adhere relatively elongated members, or strands, onto substrates. In the manufacture of a variety of bodily fluid absorbing hygienic articles including diapers, incontinence pads and other undergarments, for example, stretched elastic strands are bonded between fabrics to form waste bands and other stretchable portions thereof. In diapers, the waste bands and particularly the leg bands must provide relatively fluid tight seals between the undergarment and the body.
In known bodily fluid absorbing hygienic article manufacturing processes, adhesive is sprayed onto stretched elastic strands disposed on or very near an underlying fabric substrate moving relative to one or more adhesive dispensing nozzles. The adhesive is usually a hot melt adhesive dispensed in a swirling spiral pattern by a spiral nozzle, and is applied generously to both the substrate and the elastic strands simultaneously. The stretched elastic strand is usually bonded between overlapping fabric layers. As the stretched elastic strands contracts, the fabric adhered thereto is bunched together forming generally pleated waste bands and other stretchable portions of the undergarment. It is important that the elastic strand be bonded to the fabric substantially continuously along its axial length to ensure uniform pleating, or bunching, of the fabric, which is necessary for optimum comfort and fluid absorption, and to provide an aesthetically pleasing product.
U.S. Pat. No. 5,507,909, issued Apr. 16, 1996, entitled "Apparatus For The Manufacture Of An Elongated Element Comprising Helically Patterned Adhesive" discloses a process and apparatus for helically wrapping adhesive onto an elastic strand, which is bonded to a substrate in the manufacture of disposable absorbent products without coating adjacent areas of the substrate with large amounts of adhesive. To helically coat the elastic strand with adhesive, the strand is rotated about its axis as it is drawn past an adhesive flow from a dispensing orifice, for example by drawing the elastic strand between a nip roll assembly rotated at an angle relative thereto, or by other disclosed but less certain strand rotating means.
The known processes, however, generally apply much more adhesive onto the elastic strands and underlying substrate than is required for bonding, resulting in unnecessarily increased costs. The excess adhesive, which is usually hot, also has a tendency to deform the relatively thin, temperature sensitive fabric, thereby providing an undesirable appearance. In extreme cases the hot adhesive may destroy the fabric by burning a hole therethrough.
Another adverse effect of applying excessive amounts of adhesive onto fabrics is that the adhesive tends to stiffen the fabric. This stiffening is particularly undesirable in diaper and other undergarment applications where the elastic strand bunches the fabric to form waste bands and other stretchable portions that contact the body intimately. More particularly, the stiffened fabric tends not to bunch as freely and uniformly as it would otherwise, thereby compromising the ability of the fabric to form an effective fluid seal when stretched against the wearer's body.
The excess adhesive applied onto the fabric may also reduce the fluid absorbing capacity thereof, resulting possibly in the leakage of bodily fluids and in the accumulation of perspiratory moisture on the wearer's body, which may be particularly uncomfortable where waste and leg band portions of the garment contact the skin directly. Additionally, the adhesive stiffened fabric may be slightly abrasive against the skin, and in some extreme cases may irritate allergically sensitive skin.
The process and apparatus disclosed in the prior art U.S. Pat. No. 5,507,909 entitled "Apparatus For The Manufacture Of An Elongated Element Comprising Helically Patterned Adhesive" allegedly reduce the amount of adhesive applied to the substrate and apply more conservative amounts of adhesive onto the elastic strand, but the uniform application of adhesive helically about the strand requires consistently and uniformly controlling the rotation of the strand during the drawing thereof. It is questionable whether the elastic strand may be consistently rotated uniformly as required to uniformly apply adhesive helically thereabout in manufacturing operations. If the adhesive is not applied uniformly along the axial dimension of the strand, the stretched strand will not bond uniformly to the substrate, which adversely affects uniform bunching of the fabric. Non-uniform bunching is undesirable from an aesthetic viewpoint, and more substantively non-uniform bunching of the fabric compromises the ability of the fabric to form an effective fluid seal, and reduces the softness and comfort thereof when stretched against the wearer's body.
The present invention is drawn generally toward advancements in the art of applying fluids including adhesives onto strands, and more particularly toward bonding adhesive coated strands to substrates, especially adhesive coated elastic strands to fabrics in the manufacture of bodily fluid absorbing hygienic articles.
It is an object of the invention to provide novel methods for applying fluids to strands, and for bonding adhesive coated strands to substrates, and combinations thereof, that are economical and overcome problems in the prior art.
It is another object of the invention to provide novel methods for applying hot melt adhesives to elastic strands, and for bonding adhesive coated elastic strands to fabrics to form waist bands and other stretchable portions in the manufacture of a variety of bodily fluid absorbing hygienic articles and disposable absorbent products using reduced amounts of adhesive.
It is a further object of the invention to provide novel methods for bonding adhesive coated elastic stands to fabric substrates in the manufacture of a variety of bodily fluid absorbing hygienic articles, wherein the elastic strand is bonded to the fabric substantially uniformly along an axial length thereof to ensure uniform bunching of the fabric, thereby providing optimum comfort and fluid absorption, and an aesthetically pleasing, more marketable product.
It is yet another object of the invention to provide novel methods for reducing the amount of adhesive applied to elastic strands bonded to underlying fabric substrates in the manufacture of a variety of bodily fluid absorbing hygienic articles to reduce the possibility of melting the fabric with hot melt adhesives, to substantially eliminate fabric stiffening and to eliminate loss of moisture absorbing capacity thereof, and to reduce costs, especially costs associated with excess adhesive usage.
It is a more particular object of the invention to provide novel methods for applying fluids to a strand, useable for bonding the strand to a substrate in the production of bodily fluid absorbing hygienic articles, by drawing the strand along an isolated path, moving a fluid fiber across a path of the strand as the fluid fiber is dispensed toward the strand so that the fiber contacts the strand, and capturing substantially all of the fiber on the isolated strand. The fiber is preferably vacillated back and forth across a path of the strand, and beyond opposing sides thereof to at least partially coat all sides thereof with fluid.
It is another more particular object of the invention to provide novel methods for bonding strands to substrates in the production of bodily fluid absorbing hygienic articles by drawing the strand along a path separated spatially from the substrate, dispensing an adhesive fiber toward the strand so that at least a portion of the adhesive fiber crosses the path of the strand and contacts the strand, capturing substantially all of the adhesive fiber on the strand when the strand is spatially separated from the substrate to at least partially coat the strand with adhesive, and contacting the adhesive coated strand with the substrate to bond the strand thereto. The fiber is preferably vacillated back and forth across a path of the strand, and beyond opposing sides thereof to at least partially coat all sides thereof with adhesive.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.